Why do people root for football teams of colleges that they never attended?

It may be the local school ot they may have relatives there.

some states in the south don't have an NFL team that's local, like Alabama.  so they root for the college team.

some root for family members school.  for instance my immediate family all went to Big Ten schools.  my dad went to ohio state, so i like to root for them.  i'll root for michigan too in bowl games as long as it's not against another big ten school.

Cringe is not a noun.

I never went to Oklahoma State University, when I was a kid, my parents had retired in Mesa, Arizona, and my dad and me went to the Fiesta Bowl, which back then was a Mountain Conference bowl, before it went big. Oklahoma State played BYU and won that game, I had no idea where Stillwater was, I knew where Stillwater, Minnesota was. About 20 years later I was recruited in the medical field to Enid, Oklahoma and found out that OSU was 50 miles away so I went to a few home games, that would be after Barry Sanders.......I never saw him play......I ended up going to 5 of the 7 home games, so I thought     "why not get season tickets" I like watching them.                 So that's how I 'rooted" for them. Does that make me a "redneck" from the South??? I'm from Minnesota originally, and I can't stand Trump.

I respect people more those who are from an area and support the local team, be it college or pro, than someone who supports a team because they went to college there.  So you spent 4 years of your life there. Most of it you were probably drunk.  You have no real connection to the team 20 years later.  Quit pretending you do.  Grow up and move on with your life.